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Advanced => Plugins & Plugin Development => Programming => Nest => Topic started by: hellovn on March 30, 2014, 07:11:13 pm

Title: Nest thermostat power charged (c-wire) through usb?
Post by: hellovn on March 30, 2014, 07:11:13 pm
Hi All,

Thermostats in my house has only 2 wires (W & Rh). I have been doing some research about wifi thermostats and have a question.

1. It seems that nest thermostat may work with 2 wire systems. Do you think if it is a good idea if I can run a usb from a wall charger to my nest and have a z-wave power outlet to auto schedule my nest thermostat usb charing from 02:00 AM to 03:00 AM? The reason I do that is because nest will not be working if it is being charged by the usb port.

Running a c wire from my furnace to my thermostat will cost me around 300$ so that is not an option.

Let me know if my hack will work?

Thanks,
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: watou on March 31, 2014, 04:04:26 am
Hi All,

Thermostats in my house has only 2 wires (W & Rh). I have been doing some research about wifi thermostats and have a question.

1. It seems that nest thermostat may work with 2 wire systems....

You are correct that the Nest thermostat does not require the "C" wire.  They have a "compatibility checker" on their site that should help you review whether the Nest will work with your system. https://nest.com/thermostat/installation/#works/?mode=buy (https://nest.com/thermostat/installation/#works/?mode=buy)

watou
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: qwen3579 on March 31, 2014, 07:05:25 am
Are you wanting to run a USB charger for charging the Nest battery? I don't think you'll have to do that. I think the voltage from your Rh wire (12 volts?) charges the Nest battery.

I have a common wire in my system, but Nest support had me disconnect due to an issue I had. My system has been running fine, and charging my 2 Nests fine without it.
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: TheGadgetGuy on March 31, 2014, 10:42:20 am
The Nest will NOT accept anything significantly lower than 24v AC through the HVAC wiring to power and charge itself. 

Without major modification, you would not be able to charge the Nest via its USB connector, because the backing plate obstructs the USB connector when installed.  I had considered that myself when installing my Nest units in my motorhome, but decided against the needed modifications.



Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: jimpapa on March 31, 2014, 01:16:58 pm
I'm sitting in the Dr. Office.  So I don't have the details.  But how about if you use a separate 24v power supply and give the nest what it wants in place if the USB wiring you where going to do?

Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: dinosinc on March 31, 2014, 08:45:49 pm
try adding this http://www.smarthome.com/304AAW/Venstar-ACC0410-Add-A-Wire-Accessory-for-Programmable-Digital-Thermostats/p.aspx
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: jimpapa on March 31, 2014, 09:02:49 pm
I think Hellovn said he only has 2 wires on his current T-stats

Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: TC1 on March 31, 2014, 09:51:57 pm
If you don't want to go down the Nest route for your 2-wire thermostat, you could use the RTOA 101 available from Lowes (sold as an Iris thermostat), I have two of them, one working with a c-wire,  and one working with 2-wires and strictly off the batteries.

-TC
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: qwen3579 on April 03, 2014, 10:42:14 am
If you don't want to go down the Nest route for your 2-wire thermostat, you could use the RTOA 101 available from Lowes (sold as an Iris thermostat), I have two of them, one working with a c-wire,  and one working with 2-wires and strictly off the batteries.

-TC

Do these thermostats support controlling both from location (ie - any changes you make on one are pushed to the other)? Or have you been able to write Lua/PLEG to accomplish this?

I love my Nests, but I would like to be able to make changes from one and have it pushed to the other.
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: watou on April 03, 2014, 11:43:06 am
I love my Nests, but I would like to be able to make changes from one and have it pushed to the other.

I think there has to be a way with Lua or PLEG to achieve what you're after, but in case it's too far out of reach, the Ecobee thermostat supports this feature natively (as in, using their web console), and I wrote a plugin for that thermostat as well (http://cocu.la/vera/ecobee/README.md (http://cocu.la/vera/ecobee/README.md)).  Ecobee makes a nice range of web-accessible thermostats.
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: qwen3579 on April 03, 2014, 12:11:08 pm
I love my Nests, but I would like to be able to make changes from one and have it pushed to the other.

I think there has to be a way with Lua or PLEG to achieve what you're after, but in case it's too far out of reach, the Ecobee thermostat supports this feature natively (as in, using their web console), and I wrote a plugin for that thermostat as well (http://cocu.la/vera/ecobee/README.md (http://cocu.la/vera/ecobee/README.md)).  Ecobee makes a nice range of web-accessible thermostats.

Thanks for that info - those are pretty slick.

I have the temperature updates working on my Nests with PLEG (see here: http://forum.micasaverde.com/index.php/topic,24127.msg167381.html#msg167381 (http://forum.micasaverde.com/index.php/topic,24127.msg167381.html#msg167381)) However, luup restarts when I adjust the mode (heat, cool, auto).

Should probably move the discussion there - I didn't realize that I hijacked hellovn's thread. Sorry!  :-\
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: watou on April 03, 2014, 12:18:08 pm
I have the temperature updates working on my Nests with PLEG ... However, luup restarts when I adjust the mode (heat, cool, auto).

I wouldn't know why this is happening, but if you are doing back-to-back actions or variable changes, this might be overwhelming some aspect of Luup, socket I/O, or something else.  Would there be some way to insert a brief delay (say, 2-6 seconds) between actions that might send multiple commands off your Vera?  This is just a complete SWAG, but it's what I would try.
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: hellovn on December 09, 2014, 06:12:01 pm
I just forgot to reply this thread :). I have bought 2 z-wave 2gig CT 100 and they work great. Although they are not as luxury as Nest :)
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: RoChess on December 09, 2014, 06:55:29 pm
I'm in an old home with only 2-wires as well, but I risked trying to see if Nest would work, and it has been performing spectacular.

My only issue is with the Vera Nest plugin not yet fully supporting UI7, so I have to settle for only having automatic scene control of the Home/Away function. That supprisingly has been working out well though, the moment I get out of bed the Nest is switched to Home mode via a Vera scene, and heats the downstairs up to a comfortable temperature already before I even make it downstairs (Home set to 69F). When I go to bed it goes into Away mode and keeps temp above 50F.

Have it running for little over a month now, and already see savings on my utility bills. Am on weird ever changing schedules, so programming a regular thermostat would never have worked for me, and it would happen quite often where I had forgotten to turn the thermostat down. Having Z-Wave sensors now do that fully automatic is easy to get used to, and at this rate it should have all paid for itself in less then 6 months.
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: hellovn on December 10, 2014, 12:00:01 pm
Thanks Rochess for your information. After reading many weird problems that are reported with 2-wire NEST, i have decided to go with Z-wave battery thermostats :(. I am still a fan of NEST though so I will consider upgrading in the future.
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: RoChess on December 12, 2014, 12:16:05 am
Forgot to mention I actually was on the phone with Nest support to double check it would work for me, because I had indeed read the same horror stories.

Support tech was really knowledgable, and verified that if I measured a good AC voltage potential between the two wires that I would be good to go. Grabbed my $5 multi-meter, and measured 28V AC between R and W wires without anything connected. The Nest only draws a few miliAmps, which you could replicate with a variable resistor (potentiometer) to find out at what Ohm level the heater kicks in. That felt like too much work for me, so I just went ahead with the Amazon order.

When it arrived I simply secured the R+W wires with shrinkwrap to feed them through the Nest wallplate without having to pop the breaker; followed by inserting each wire into the Nest backplate, and clicking on the Nest unit itself into the backplate. Display came to live, and I immediatly began to configure it for WiFi/etc.

Inside Vera UI7 -- via the Nest app/plugin -- I can monitor the Nest thermostat battery level in an easy way, and it usually hovered between 85% and 98% during the initial week of messing about. I did forget to check battery level right after unboxing, so by the time I had Vera app configured the battery was already at 100% (possibly already was). Keep in mind that the reason battery dropped so low to 85%, was because I am using an aggressive 60 second poll timer value to update status, and was constantly changing/verifying settings via the LCD display on the Nest (as well as via browser/Vera).

With things settled in now, and relying more on Vera scene control versus manually rotating that awesome control knob, it sits at 100% charged pretty much all the time now (just checked).

I did in the end have to disable the auto-away scheduler of Nest, after 14-days of training it was nowhere near understanding my schedule. This probably saves more Nest battery usage.
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: Javelin on June 11, 2015, 06:53:11 am
Hi wondering if any knowledgable sparkys be able to help me.

I purchased a nest for my Braemar TH325 Ducted heating Unit

Ive currently got the unit wired using R,RH and added a C Wire

It works however even though my wires read 24volts I'm not getting enough juice or battery is deciding not to charge on my nest.

Im only reading a VOC of 14.10 in the thermostat settings on the wires, when it says I need between 20-40 on nest website. So iI presuming my voltage is not right somewhere so I thought id eliminate the furnace leaching from the equation by adding my own transformer.

As im in australia its hard to find a power supply to provide the correct voltage. But I managed to track down this one only question is 1Amp to much or to little for my nest circuit board?

http://www.jaycar.com.au/Power-Products-Electrical/Plugpacks/AC-Output/Mains-Adaptor-24VAC-1A-Unregulated-Bare-Ends/p/MP3032

I plan to just replace the 1 wire on the C circuit and see if that works or possible try it on the RC circuit + C wire. Im scared of crossing circuits and damaging my furnance if anyone could advise would be appreciated.
Title: Nest thermostat power charged (c-wire) through usb?
Post by: Brientim on June 11, 2015, 03:27:00 pm
Have a read here. 

I have central gas heating (in Oz) which has the C but manual thermostat had 2 wires,.  look at the furnace  and you may find you a surprise.

http://smartthermostatguide.com/thermostat-c-wire-explained/
Title: Re: Nest thermostat power charged (c-wire) through usb?
Post by: Javelin on August 21, 2015, 07:13:01 am
Can Confirm that the Jaycar Transformer works. I ran the Red wire to Rc and black to C. Then connected my two heater wires to RH and W1. Battery voltage running at full in no time! Vin and Voc both up around 33-37 and 100ma

Now running with clicking sound, full brightness and wake screen on approach. Unit seems alot more responsive aswell.

Both Temps also showing under Ui7 with the new nest plugin Couldn't be happier!

http://www.jaycar.com.au/Power-Products-Electrical/Plugpacks/AC-Output/Mains-Adaptor-24VAC-1A-Unregulated-Bare-Ends/p/MP3032